GDNF and myeloid sarcoma: Genes on the human X chromosome include genes for reproduction and a disproportionately large number that code for brain function, such as the BEX family (brain expressed X-linked genes), NF2 (neurofibromin 2), GDNF (glial cell derived neurotrophic factor) and PLP1 (myelin proteolipid protein, the most abundant protein in CNS myelin, an autoantigen for EAE, and a target of immune attack in MS (153, 154)).